1. Field of the Invention
The present invention relates to an automotive braking system having both brake-by-wire and conventional braking capability.
2. Disclosure Information
In automotive brake-by-wire systems, such as those in use with hybrid vehicles having both friction braking and regenerative braking, it is known to provide a pedal feel simulator to replicate the force/displacement response of a conventional hydraulic brake system. Such pedal feel simulator devices are installed in an effort to obtain transparency to the vehicle driver regarding the type of braking mode used by the vehicle at any particular time. In other words, the amount of pedal force required from a motorist to produce a given rate of vehicle deceleration should not change when regenerative braking is present.
In the event that a drive-by-wire portion of a system becomes unavailable, such as is sometimes the case when, for example, a regenerative braking system has fully recharged an energy storage device, or if a braking system impairment limits the ability to provide assisted braking, it is necessary to rely upon the conventional hydraulic brakes. In such case, it is desirable to eliminate the resistive portion of brake pedal force which would otherwise be provided by a pedal feel simulator. This prevents the motorist from having to overcome not only brake pedal force arising from the master cylinder, but also the force arising from the pedal feel simulator.
Known pedal feel simulators typically use electrohydraulic devices to selectively couple the simulator into and out of the braking system. Unfortunately, such electrohydraulic devices offer high first cost and high maintenance costs, and require complicated electronic systems support to assure their continued operation.
It would be desirable to provide a brake-by-wire type of braking system with a simplified and easily controllable pedal feel simulator.